This invention is generally directed to toner and developer compositions, and more specifically, the present invention is directed to developer and toner compositions, including low melting toner compositions containing novel anisotropic or thermotropic liquid crystalline polyimide resins, and process for the preparation thereof. In embodiments, there are provided in accordance with the present invention, toner compositions comprised of thermotropic liquid crystalline polymide resins, or anisotropic polyimide resins, and pigment particles comprised of, for example, carbon black, magnetites, or mixtures thereof, cyan, magenta, yellow, blue, green, red, or brown components, or mixtures thereof thereby providing for the development and generation of black and/or colored images. In embodiments, there are provided in accordance with the present invention anisotropic or thermotropic liquid crystalline polyimide toner resins of the following formula and processes for the preparation thereof by melt condensation ##STR2## wherein X is a symmetrical mesogenic moiety or a cycloaliphatic radical attached to four imide carbonyl moieties, for example X can be ##STR3## R is alkyl, alkylene with from about 1 to about 25 carbon atoms, such as methyl, ethyl, propyl, butyl, methylene, ethylene, propylene, butylene and the like, and preferably 1 to about 15 carbon atoms, oxyalkylene or polyoxyalkylene containing from about 1 to about 25, and preferably 1 to about 15 carbon atoms, and more specifically diethylene oxide, triethyleneoxide or polyoxypropylene, and the like; and m represents the number of segments and can be a number of from about 1 to about 10 to about 10,000. The X in the above formula can be phenyl, naphthyl, cyclohexyl, or bicycloaliphatic. The toner compositions of the present invention in embodiments possess a number of advantages, including low melting characteristics, blocking characteristics, possess excellent admix characteristics, have excellent nonvinyl-offset properties, and a low relative humidity sensitivity such as from about 1.01 to about 2.3. The resin composition of the present invention can in embodiments be generated by a process involving the melt polycondensation of about 1 mole equivalent of a symmetrical mesogenic dianhydride such as pyromellitic dianhydride (1,2,4,5-benzene tetracarboxylic dianhydride) or naphthalene dianhydride, and the like, and about 1 mole equivalent of an alkylene diamine, or preferably a diamino terminated alkylene oxide, such as a diaminoterminated polypropylene oxide or diaminoterminated polyethylene oxide, available from Texaco Chemicals as JEFFAMINE D-230.TM., D-400.TM., D-700.TM., EDR-148.TM., and EDR-192.upsilon. as illustrated by the formulas ##STR4## wherein EDR-148 n=2; R=H
EDR-192 n=3; R=H PA1 D-230 n=2,3; R=CH.sub.3 PA1 D-400 n=5,6; R=CH.sub.3
The aforementioned liquid crystalline polyimides of the present invention in embodiments exhibit a number average molecular weight of from about 1,500 to about 50,000, and preferably 20,000 grams per mole as measured by vapor phase osmometry, with a glass transition temperature of from about 40.degree. C. to about 80.degree. C., and more preferably of from about 50.degree. C. to about 65.degree. C. as measured by the Differential Scanning Calorimeter. In embodiments, the thermotropic liquid crystalline polyimide can be generated by a process of selecting from about 0.7 mole equivalent to about 1 mole equivalent of symmetrical mesogenic dianhydride, such as pyromellitic dianhydride, and from about 0.7 to about 1 mole equivalent of an alkylene diamine, or preferably a diaminoterminated alkylene oxide, such as the diaminoterminated polypropylene oxide or diaminoterminated polyethylene oxide available, from Texaco Chemical as JEFFAMINE.TM., and optionally a kinking agent, such as a nonsymmetrical aromatic or cyclic monomer such as 1,3-cyclohexyldiamine present in an amount of from about 0.1 mole equivalent to about 0.3 mole equivalent and which depresses the liquid crystalline phase to a narrower liquid crystalline range, such as from about 1 to about 20.degree. C. and which polymide resin possesses a number average molecular weight of from about 1,500 to about 50,000 grams per mole as measured by vapor phase osmometry, and with a glass transition temperature of from about 40.degree. C. to about 70.degree. C., and more preferably from about 50.degree. C. to about 64.degree. C. as measured by the Differential Scanning Calorimeter.
Examples of advantages of the toner composition of the present invention include low fusing temperatures, such as from about 120.degree. C. to about 140.degree. C., thus lower fusing energies are needed for fixing enabling less power consumption during fusing, and permitting extended lifetimes for the fuser system selected. Furthermore, the toner compositions of the present invention possess in embodiments a broad fusing latitude, such as from about 40.degree. C. to about 100.degree. C., with minimal or no release oil, which oil inhibits the toner from offsetting onto the fuser rollers usually associated with ghosting or background images on subsequent copies. Furthermore, the fused images obtained with the toner compositions of the present invention in embodiments do not substantially offset to vinyl covers, such as those utilized for notebook binders, and possess low humidity sensitivity ratio of from about 1 to about 2.3 calculated by the ratios of the triboelectric charge in microcoulombs per gram of the developer after being placed in a chamber of 20 percent humidity for 48 hours; to the triboelectric charge in microcoulombs per gram of the developer after being placed in a chamber of 80 percent humidity for 48 hours.
In designing resins for a toner composition, it is generally desired that the glass transition temperature of the resin be from about 50.degree. C. to about 65.degree. C., and preferably no less than about 55.degree. C.; therefore, for example, the toner particles should not aggregate, coalesce or block during manufacturing, transport or storage process or until the toner is needed for fixing. Additionally, low fusing characteristics can be important, hence the resin should melt or flow a low temperature, such as from about 130.degree. C. to about 145.degree. C. Moreover, low relative humidity sensitivity of toners is desired such that the triboelectric charge is stable to changes in environmental humidity conditions. Copiers and printers equipped with two component developers, that is a toner as one component mixed with the carrier as the other component, can exhibit a positive or negative triboelectric charge with a magnitude of from about 7 microcoulombs per gram to about 40 microcoulombs per grams. This triboelectric charge permits the toner particles to be transferred to the latent image of the photoreceptor with an opposite charge, thereby forming a toned image on the photoreceptor, which is subsequently transferred to a paper or a transparency substrate, and thereafter subjected to fusing or fixing process. In these development systems, it is important for the triboelectric charge to be stable under differing environmental humidity conditions such that the triboelectric charge does not change by more than from about 5 to about 10 microcoulombs per gram. A change of more than from about 5 microcoulombs per gram to about 10 microcoulombs per gram in triboelectric charge of the toner developer can cause nonuniform toned images or result in no toning of the photoreceptor, thus unbalanced density or gray scale is observed in the developed images, or no developed images at all result. Generally, humidity ranges may differ from less than about 20 percent in dry regions to more than about 80 percent in humid regions, and some geographical regions may exhibit fluctuations of up to from about 50 to about 80 percent humidity level within the same day. In such climates, it is important that the developmental triboelectric charge does not change by more than from about 5 microcoulombs per gram to about 10 microcoulombs per gram. As toner resins generally represent from about 80 percent to about 98 percent by weight of toner, the resin sensitivity to moisture or humidity conditions should be minimized thereby not adversely affecting the triboelectric charge thereof. A number of toner polymeric resins utilized as toner compositions, such as for example styrene-acrylates, styrene-methacrylates, styrene-butadienes and especially polyesters contain from about 0.1 to about 2 percent by weight of moisture, and in many instances, the moisture content of polyesters may change from about 0.1 to about 4 percent by weight at humidity levels ranging from about 0 to about 100 percent, or preferably from about 20 percent to about 80 percent humidity. These changes in moisture content of the resin may have a dramatic adverse effect on the triboelectric charge of the toner developer. Relative humidity sensitivity of toner is customarily measured by first fabricating a toner comprised of a pigment, optional charge control agent and a resin, then admixing the toner from about 3 percent by weight to about 7 percent by weight with a carrier. The developer composition is then subjected to various humidity level in a sealed chamber for a finite period of time, such as about 48 hours. The triboelectric charge is then measured for the same developer composition with differing humidity levels and analyzed by several methods, such as graphing the triboelectric charge as a function of humidity level and observing the regions in which dramatic changes occur Another measuring method comprises dividing the aforementioned graphical interpolation of tribo vs humidity level in three regions, wherein region A is from about 0 to about 30 percent humidity, region B is from about 30 to about 65 percent humidity, and region C is higher than about 65 percent humidity to about 100 percent. Since these measurements are cumbersome and require timely consuming measurements, there can be measured the triboelectric charge after subjecting the toner developer composition to two humidity levels, such as 20 percent humidity and 80 percent humidity, and then calculating the relative sensitivity by taking the triboelectric charge ratio of the 20 to 80 percent humidity as given by the following ##EQU1## wherein RH is the relative humidity.
Thus, if the relative sensitivity is about 1.0, the toner composition is nonhumidity sensitive, whereas if the relative sensitivity is greater than from about 3, or greater than about 5, the toner composition is said to be very humidity sensitive. It is generally believed that a number of polymeric materials exhibit relative sensitivity greater than 1.0, and in general, styrene butadiene, or styrene acrylate possess relative humidity sensitivity of greater than 1.0 and less than about 2.5, whereas polyesters possess a relative humidity sensitivity of greater than 1.8 and less than about 5. Hence, an advantage of the styrene-acrylate or styrene-butadiene class of resins over polyesters is their lower relative sensitivity. Polyesters are known to display advantages over styrene based resins, such as low fixing temperatures of from about 120.degree. C. to about 140.degree. C., high gloss, such as from about 50 gloss units to about 80 gloss units, and nonvinyl offset properties. Therefore, there is a need for toner compositions comprised of a resin which possess all of the aforementioned advantages, such as low fixing of from about 120.degree. C. to about 140.degree. C., high gloss, such as from about 50 gloss units to about 80 gloss units, nonvinyl offset properties and in addition low relative humidity sensitivity, such as from about 1.0 to about 2.0. These and other advantages are attained in embodiments by the toner compositions of the present invention comprised of a pigment, optionally a charge control agent and a thermotropic liquid crystalline polyimide resin derived from a mesogenic dianhydride and organodiamine, which toner exhibits low fixing of from about 120.degree. C. to about 140.degree. C., high gloss, such as from about 50 gloss units to about 80 gloss units, nonvinyl offset properties and low relative humidity sensitivity, such as from about 1.0 to about 2.3.
Thermotropic liquid crystalline resins are known, such as those illustrated in U.S. Pat. No 4,543,313, the disclosure of which is totally incorporated herein by reference, which discloses toner and developer compositions with thermotropic liquid crystalline polyesters, polyamides, and polycarbonates. The '313 patent does not mention tetrasubstituted monomers such as pyromellitic anhydride, diamino alkane or diaminoalkylene oxides. Liquid crystalline polyesters and polyarylates are also known, such as disclosed in U.S. Pat. Nos. 4,891,293; 4,973,539; 5,039,773; 5,082,919 and 4,954,412 wherein the polyesters are comprised of at least two and preferably three spacer moieties.
Polyimide resins and, more specifically, liquid crystalline polymide resins are also known such as summarized and illustrated in the Encyclopedia of Polymer Science and Engineering, 2nd edition, Volume No. 12, published by Wiley (1985). However, the polyimide resins mentioned are believed to be fully aromatic and useful as high performance materials, and no mention for use as toners is described. Also, liquid crystalline polyimide with flexible diamino alkane moieties and, more specifically, polyoxyalkylene moieties are not mentioned.
Illustrated in the following copending applications, the disclosures of each being totally incorporated herein by reference, are:
U.S. Ser. No. 144,075, illustrates a toner composition comprised of a pigment and a crosslinked polyimide; and wherein the crosslinked polymide can be obtained from the reaction of a peroxide with an unsaturated polymide of the formula ##STR5## R is alkyl or oxyalkylene and m represents the number of monomer segments present and is a number of from about 10 to about about 1,000.
U.S. Ser. No. 144,956, illustrates a toner composition comprised of pigment, and polyimide of the formula ##STR6## wherein n represents the number of monomer segments, and is a number of from about 10 to about 1,000; and R is alkyl, oxyalkyl, or polyoxyalkyl.
U.S. Ser. No. 144,964, illustrates a toner composition comprised of pigment, and a polyester imide resin of the formula ##STR7## wherein n represent the number of segments present and is a number of from about 10 to about 10,000; R' is alkyl or alkylene; and R is independently selected from the group consisting of an oxyalkylene and polyoxyalkylene.
U.S. Ser. No. 144,918, illustrates a toner composition comprised of pigment, and polyimide of the formula ##STR8## wherein m represents the number of monomer segments present; X is ##STR9## thus X can be benzophenone, oxydiphthalic, hexafluoropropane diphenyl, diphenyl sulfone, or biphenyl; and X is attached to four imide carbonyl moieties; and R is independently selected from the group consisting of alkyl, oxyalkylene and polyoxyalkylene.